Technical Field
The present disclosure relates generally to the field of wood treatment apparatus, and methods of use, and more specifically to wood and wood composite heat treatment systems, and methods of their use, particularly for heat treating such materials used for furniture and flooring.
Background Art
Typically natural wood or composite materials either have chemicals applied or are intrinsically moisture-laden (either so-called “free” moisture or “fiber” moisture, or both). Wood for furniture making and wood used for flooring may be subjected to one or more of various processes, including curing, kiln-drying, conditioning, and the like, first to cure the chemicals and drive out volatiles and naturally existing moisture. Because of the combustibility of wood, major challenges are presented to design an oven for moisture processing.
Various types of ovens and methods are used for drying plywood, laminated wood or natural wood, all generally comprising a box or container defining a treatment zone, and including exhaust fans, heating means such as burners for direct heating of circulating air, use of stickers for spacing the boards, and air circulation fans. Some systems and methods include movable supports for the wood, for example carts or actual rail cars movable upon rails. Some ovens include grills or fins on inlet and/or outlet of air blowers to convert turbulent flows into laminar flows, or use of panels with spoilers with certain shape. One technique consists in using the energy available in a large wood products plant, such as a steam boiler, to supply steam to tubes internal of or external of the treating oven, where air is blown around the tubes to heat the air, and then through a stack of wood products in a cross-circulation flow pattern. In some techniques and ovens, or entire warehouses, the cross-circulation flow direction may be reversed periodically. In other techniques, the floor or supporting panels for the wood are heated by steam tubes or electrical wires. In yet other techniques, microwaves may be used to treat the wood (kill insects) and heat the wood.
As noted herein, the predominant technique is to employ direct-heated air in cross-circulation flow of the air through separated wood pieces, such as boards or panels separated by stickers, where flow direction is periodically reversed. While fairly efficient for creating wood boards or panels of homogenous moisture quantity, this technique either requires manual switching of flow direction, which would be counterproductive or even hazardous if left un-switched, or complicated, expensive controllers and algorithms based on moisture sensors, temperature sensors, and the like. This limits the applicability of the technique to a limited number of operations where the same species of wood is processed every time, and therefore operation may be based on known or only slightly varying moisture levels in the feedstock. Another drawback of this technique (according to the known art) is that the combustion products from combustion burners flowing in the circulating air may have a deleterious effect on the wood, depending on the fuel and oxidant used, which would also be counterproductive.
It would be an advanced in the wood treatment art, and in particular the art of combustion-based heat treating and/or moisture treating of wood and wood products, to improve energy usage and/or safety while avoiding direct contact of the combustion products with the product being treated.